In order to make engine powered vehicles more energy efficient, in addition to implementing various technologies that improve the energy consumption of the engine itself, vehicle and engine manufacturers also try to reduce the weight of the various components of the vehicle, including the engine.
Pistons are one of the most important components of reciprocating internal combustion engine. The pistons transfer the energy of the expanding combustion gases in the combustion chamber to the crankshaft of the engine, thereby causing the crankshaft to turn. However, the pistons also represent a significant amount of the reciprocating masses of the engine.
For this reason, in many engines, the steel from which the pistons were traditionally made has been replaced with aluminum. In addition to being lighter in weight, aluminum pistons are also less expensive and provide good heat conductivity characteristics.
One of the disadvantages of aluminum pistons is that they are less resistant to high temperatures than steel pistons. The overheating of a piston can lead to deformation and cracking of the crown of the piston and to ductile deformation of the pin bosses used to attach the piston to the connecting rod.
High temperatures of the pistons can be the result of many different factors. For example, high power output engines tend to be hotter. In order to achieve low emissions and low fuel consumptions, many engine manufacturers opt for a lean air-fuel mixture to be combusted in the combustion chambers, which results in higher temperature combustion engines. In carbureted two-stroke engines, a fuel mixed with air flows in the crankcase that can absorb some of the heat from the pistons. However, some two-stroke engines now employ direct fuel injection technology where the fuel is injected directly in the combustion chambers. As a result, there is no more fuel flowing in the crankcase that could absorb heat from the pistons, and therefore the pistons get hotter. As such, aluminum pistons may not be suitable in engines having one or more of the above-described characteristics.
Therefore, there is a need for a relatively lightweight piston having good heat resistance characteristics.